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Computer says no, generation, VS good old fashioned common sense based on time served experience and knowledge.
BMW MINI developed a coolant leak only when hot, the coolant was collecting on top of the gearbox, directly above the gearbox is the two stage electro thermostat, upon a visual it was blindingly obvious the thermostat housing was the culprit, a hairline crack had developed over the many heat cycles over the years, expanding enough when hot to allow a small leak whilst under normal pressurised operating condition, once cooled the hairline crack self sealed.
My self diagnosis was confirmed at my local MINI dealership, a new electro thermostat was fitted, coolant topped up and presumably the workshop technician bled all air from the coolant system, ran the engine to operating temperature, waited for the electro thermostat to open to fully circulate the coolant, whilst triggering the coolant fan on, and continue to run the engine until the coolant fan switched to off, triggered by the closing of the electro thermostat, all basic procedure when dealing with any coolant system.
It transpired that this basic of basic procedures was not done, as less than a week later, the coolant expansion bottle was empty, this visual of the coolant expansion bottle was triggered by the lack of heat in the heating system in the car, there was no coolant leak evident, the coolant was topped up, the heating system was still hit and miss, heat some days, no heat on other days.
Further visuals of the coolant system after every journey indicated absolutely no external coolant leak or indeed any loss of coolant from the expansion bottle, hmmm intriguing, I hear lots of you saying head gasket, again there was no evidence to indicate head gasket failure, no over pressurisation of the coolant system, no coolant loss, no emulsification of the oil system, no emulsified odour either in the coolant or oil, to indicate signs of compression contamination, hmmm intriguing.
Sometimes being technically minded goes against you, I was now over thinking, I had just about every possibility racing through my mind, maybe a hairline crack in either the cylinder head coolant jacket, maybe a hairline crack in the block coolant jacket, maybe the new thermostat was faulty, not opening at all, maybe the water pump impeller shaft shaft had broken, and although the external water pump drive pulley was spinning, the impeller could be stationary due to a broken shaft !!
At this stage, without wanting to continue any further self diagnosis, strip down of components etc etc, I stepped back, stopped over thinking, or tried to, and went back to basics, we had no external coolant leak, there was no obvious internal engine leak, no heating system leak into the car, no coolant over pressurisation, I then had the engine idle waiting for the coolant fan to be triggered by the opening of the coolant electro thermostat, after what was way too long, the thermostat should have opened and the coolant fan should have triggered on and off, completing a normal coolant operating cycle.
Everyone still following this, good, I then touched the coolant top hose, which fed from the electro thermostat to the radiator inlet, this was very hot to the touch, quite normal, I reached in to the radiator itself, and to my surprise, the radiator at the top was only just about tepid to the touch, but only at the very top, first two or three rows, then cold all the way to the bottom of the radiator, hmmm this should have been as hot as the top hose itself, I then reached under the car, touched the bottom coolant hose, this was full of coolant yet absolutely cold, no heat whatsoever, hmmm.
This to me and many others would now indicate a failure of the coolant radiator from internal Aluminium corrosion, blockage etc etc, yet the coolant showed no sign of corrosion debris, what next, coffee break and head scratching, back to overthinking, I know exactly how the coolant system operates on the BMW MINI's and coolant systems in general, I now start processing how any of the coolant systems electrical sensors could be the cause for what is now looking like an internal flow issue, the heating system valve is fully operational, as is the electro thermostat sensor which triggers the coolant fan, yet the coolant fan never triggers, the coolant fan is free to rotate, I can trigger it manually, so all good, hmmmm.
During all this investigation I have noticed that the coolant overflow return does indeed have positive flow, indicating that the thought of the water pump impeller shaft being broken is not the issue, so why no flow ?
I've gone over and over the complete system in my head and physically on the MINI, my mind is made up, the coolant radiator has collapsed internally, restricting flow, the coolant flow simply recycles through the heater matrix and not the engine coolant radiator, simple as that, or so I thought, hmmm still thinking.
I then make the call to my local MINI dealer, relay the whole story from the time they fit the electro thermostat, including my self diagnosis that the coolant radiator will need replacing, furthermore, because I'm a good customer and my expertise is recognised, and I've even solved issue that their technicians can't diagnose, they agree to fault find FOC, great news for me.
Two days on, I'm still overthinking the coolant issue, it's also got the MINI dealership scratching their heads, as is usual today, the computer diagnosis showed no stored fault codes, and so that indicates to the young or less experienced technician, there can not be a fault !!
We are now at a stage where the most experienced technician/service manager is holding his hands up with the conclusion that there is NO fault, all because the computer says NO, what next ?
What next, good old fashioned stage by stage thought of just how each component operates, now modern engines require fast warm up to meet strict stringent emission figures, to allow for fast warm up, you need to close down coolant flow, this on the BMW MINI engines is done with a two stage electro thermostat, an electronic controlled water pump, this is controlled by a self heat regulating friction wheel, which is not driven from the ancillary drive belt directly by a pulley wheel, it is as the name suggests, driven by friction applied force to the outer of the drive belt, as this friction wheel is electronically controlled through the ECU, it's mechanical applied force is a constant under normal operation, which pulses in and out as demanded by the temperature parameter control in the ECU.
So with all the mechanical components in working order, all electronic sensors sending correct signals, a radiator which has not internally collapsed allowing a blockage, there is still no coolant circulation flow observed whilst the engine idles or fast idles !!
After lots of head scratching, overthinking and discussions including testing another MINI with the same engine, specifications etc, which also resulted with the apparent lack of coolant circulation flow, cold radiator/bottom hose etc, the general consensus from my local BMW MINI dealership is, that somewhere along the road of software updates, BMW MINI have altered the engine operation temperature parameter control for emissions !!
I'm NOT convinced of this diagnosis, and will continue to give this issue further thought, that said, once my local BMW MINI dealership workshop sign off their diagnostic results, as NFF (no fault found) after exhaustive testing, the onus will be on them, should a coolant issue occur in the future, however, even with the onus on BMW MINI, I will have a hard time proving onus.
TBC.....
BMW MINI developed a coolant leak only when hot, the coolant was collecting on top of the gearbox, directly above the gearbox is the two stage electro thermostat, upon a visual it was blindingly obvious the thermostat housing was the culprit, a hairline crack had developed over the many heat cycles over the years, expanding enough when hot to allow a small leak whilst under normal pressurised operating condition, once cooled the hairline crack self sealed.
My self diagnosis was confirmed at my local MINI dealership, a new electro thermostat was fitted, coolant topped up and presumably the workshop technician bled all air from the coolant system, ran the engine to operating temperature, waited for the electro thermostat to open to fully circulate the coolant, whilst triggering the coolant fan on, and continue to run the engine until the coolant fan switched to off, triggered by the closing of the electro thermostat, all basic procedure when dealing with any coolant system.
It transpired that this basic of basic procedures was not done, as less than a week later, the coolant expansion bottle was empty, this visual of the coolant expansion bottle was triggered by the lack of heat in the heating system in the car, there was no coolant leak evident, the coolant was topped up, the heating system was still hit and miss, heat some days, no heat on other days.
Further visuals of the coolant system after every journey indicated absolutely no external coolant leak or indeed any loss of coolant from the expansion bottle, hmmm intriguing, I hear lots of you saying head gasket, again there was no evidence to indicate head gasket failure, no over pressurisation of the coolant system, no coolant loss, no emulsification of the oil system, no emulsified odour either in the coolant or oil, to indicate signs of compression contamination, hmmm intriguing.
Sometimes being technically minded goes against you, I was now over thinking, I had just about every possibility racing through my mind, maybe a hairline crack in either the cylinder head coolant jacket, maybe a hairline crack in the block coolant jacket, maybe the new thermostat was faulty, not opening at all, maybe the water pump impeller shaft shaft had broken, and although the external water pump drive pulley was spinning, the impeller could be stationary due to a broken shaft !!
At this stage, without wanting to continue any further self diagnosis, strip down of components etc etc, I stepped back, stopped over thinking, or tried to, and went back to basics, we had no external coolant leak, there was no obvious internal engine leak, no heating system leak into the car, no coolant over pressurisation, I then had the engine idle waiting for the coolant fan to be triggered by the opening of the coolant electro thermostat, after what was way too long, the thermostat should have opened and the coolant fan should have triggered on and off, completing a normal coolant operating cycle.
Everyone still following this, good, I then touched the coolant top hose, which fed from the electro thermostat to the radiator inlet, this was very hot to the touch, quite normal, I reached in to the radiator itself, and to my surprise, the radiator at the top was only just about tepid to the touch, but only at the very top, first two or three rows, then cold all the way to the bottom of the radiator, hmmm this should have been as hot as the top hose itself, I then reached under the car, touched the bottom coolant hose, this was full of coolant yet absolutely cold, no heat whatsoever, hmmm.
This to me and many others would now indicate a failure of the coolant radiator from internal Aluminium corrosion, blockage etc etc, yet the coolant showed no sign of corrosion debris, what next, coffee break and head scratching, back to overthinking, I know exactly how the coolant system operates on the BMW MINI's and coolant systems in general, I now start processing how any of the coolant systems electrical sensors could be the cause for what is now looking like an internal flow issue, the heating system valve is fully operational, as is the electro thermostat sensor which triggers the coolant fan, yet the coolant fan never triggers, the coolant fan is free to rotate, I can trigger it manually, so all good, hmmmm.
During all this investigation I have noticed that the coolant overflow return does indeed have positive flow, indicating that the thought of the water pump impeller shaft being broken is not the issue, so why no flow ?
I've gone over and over the complete system in my head and physically on the MINI, my mind is made up, the coolant radiator has collapsed internally, restricting flow, the coolant flow simply recycles through the heater matrix and not the engine coolant radiator, simple as that, or so I thought, hmmm still thinking.
I then make the call to my local MINI dealer, relay the whole story from the time they fit the electro thermostat, including my self diagnosis that the coolant radiator will need replacing, furthermore, because I'm a good customer and my expertise is recognised, and I've even solved issue that their technicians can't diagnose, they agree to fault find FOC, great news for me.
Two days on, I'm still overthinking the coolant issue, it's also got the MINI dealership scratching their heads, as is usual today, the computer diagnosis showed no stored fault codes, and so that indicates to the young or less experienced technician, there can not be a fault !!
We are now at a stage where the most experienced technician/service manager is holding his hands up with the conclusion that there is NO fault, all because the computer says NO, what next ?
What next, good old fashioned stage by stage thought of just how each component operates, now modern engines require fast warm up to meet strict stringent emission figures, to allow for fast warm up, you need to close down coolant flow, this on the BMW MINI engines is done with a two stage electro thermostat, an electronic controlled water pump, this is controlled by a self heat regulating friction wheel, which is not driven from the ancillary drive belt directly by a pulley wheel, it is as the name suggests, driven by friction applied force to the outer of the drive belt, as this friction wheel is electronically controlled through the ECU, it's mechanical applied force is a constant under normal operation, which pulses in and out as demanded by the temperature parameter control in the ECU.
So with all the mechanical components in working order, all electronic sensors sending correct signals, a radiator which has not internally collapsed allowing a blockage, there is still no coolant circulation flow observed whilst the engine idles or fast idles !!
After lots of head scratching, overthinking and discussions including testing another MINI with the same engine, specifications etc, which also resulted with the apparent lack of coolant circulation flow, cold radiator/bottom hose etc, the general consensus from my local BMW MINI dealership is, that somewhere along the road of software updates, BMW MINI have altered the engine operation temperature parameter control for emissions !!
I'm NOT convinced of this diagnosis, and will continue to give this issue further thought, that said, once my local BMW MINI dealership workshop sign off their diagnostic results, as NFF (no fault found) after exhaustive testing, the onus will be on them, should a coolant issue occur in the future, however, even with the onus on BMW MINI, I will have a hard time proving onus.
TBC.....
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